I don't know if this will generate many examples that don't fall under subtropes, but seems like a case of Missing Supertrope Syndrome. Simply put, two characters who aren't in a romantic relationship pretend to be. Naturally, there's a high likelihood of them Becoming the Mask, or at least one character claiming It Meant Something to Me. Supertrope of Undercover as Lovers, Operation: Jealousy, The Beard, Citizenship Marriage, Shock Value Relationship, Boyfriend Bluff. Contrast Secret Relationship. See also Fake-Out Make-Out, Marriage Before Romance (when the fake relationship becomes real) and Marriage of Convenience.
Examples:Anime and Manga
- The premise of Nisekoi, translated as "False Love". The lead characters are pressured into pretending to be in a romantic relationship to keep their Feuding Families from getting out of hand.
- In Scum's Wish, Hanabi Yasuraoka and Mugi Awaya are going out together, but the couple loves someone else — their teachers.
- Ranma ½ has a variant. After Ukyo mistakes Ranma's guilt induced kindness as affection she tries getting closer to him and even starts living with him. So in order to get Ukyo to leave, Ranma and Akane are forced to pretend to already be married, when they're actually just reluctantly engaged at that point. It doesn't fool Ukyo though who keeps making moves towards Ranma.
- In Koi to Uso, there are severe social consequences for not going through with your Bureaucratically Arranged Marriage. Yajima and his arranged fiance feel no connection and haven't willingly spent time together in years (in large part because he still loves his ex-girlfriend), but both claim to be in love and ready to marry any day because otherwise their careers would be in jeopardy.
- Get Smart: Two KAOS agents once pretended to be in love, sharing a public kiss to escape detection by CONTROL. Max and 99 likewise often masqueraded as a married couple on missions before they got hitched for real.
- Booth and Brennan did this several times on Bones before getting together for real. They went undercover as "Buck and Wanda" a couple of times, and once they did it at Brennan's school reunion.
- The premise of the britcom Spaced is that the main characters believe they have a Single-Issue Landlord who will only rent the flat to a couple. It eventually turns out this was all based on a misprinted advertisement.
- Frasier pretends to be Roz's date at a family reunion when she's recently been dumped and can't face her competitive, passive-aggressive sisters.
- Martin pretends to date the mother of Frasier's Sitcom Arch-Nemesis as a prank on the pair of them.
- In Victor/Victoria, when Victoria starts masquerading as the female impersonator Victor, she and Toddy pretend to be lovers.
- Fry on Futurama gets himself into a fake relationship triangle. First he pretends to be Amy's boyfriend so that her parents would stop trying to set her up with men. Later he pretends to be Leela's boyfriend so that Zapp Brannigan will stop hitting on her. This becomes awkward when all of them are having dinner at the captain's table in front of both Amy's parents and Zapp.
- South Park: In the episode "About Last Night", it is revealed that Barack Obama and Michelle Obama aren't actually married, but it is all a ruse for getting Obama into office so he and McCain can steal an expensive diamond. At the end of the episode, Barack decides to be president after all and asks Michelle to stay with him.
- In The Proud Family, Penny and Sticky get into one of these because the former (begrudgingly) wanted to assist the latter in gaining back Dijonay's affections for him.
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